A field-effect transistor (FET), which is a fundamental element of digital integrated-circuits, is comprised of three-terminal architecture and functions as a small amplifier to amplify gate signal by modulating the resistance between source and drain. Substantial efforts have been put on minimization of FET in order to integrate more units to increase chip performance and lower power consumption. All the improvements thus far have been restricted to optimization by using alternative materials, shape design, etc., which progresses slowly toward the unit size limitation. To eventually overcome this limitation, architecture level redefinition to substantially reduce FET size is highly desired.
Besides applications in logic circuits, FETs are widely used in sensors, acting as readout electronic component of sensor pixel to amplify sensed electrical signals. Referring now to FIG. 1, the pixel of an image sensor, the digitalizing electronics of vision information that dominates human's recognition of the world, is typically composed of a plurality of discrete components including a photo-detector diode (PD) that converts optical information into an electrical signal and one or more FETs to further amplify the electrical signal. FIG. 1 illustrates an exemplary structure of a CMOS pixel, comprised of a photodiode (PD) to convert a photo signal into an electrical signal, a field-effect transistor (FET) to further amplify the converted electrical signal, and corresponding multi-interconnection layout. Such sensor architecture has seen very little change since its inception, and has generally been kept intact even for the pixel miniaturization process. This traditional sensing scheme not only requires complicated integration of multi-functional components in one pixel, but also inherently induces noise during the signal converting and electrical amplifying dual processes, which directly results in low resolution and weak sensitivity.
Therefore, what are needed are devices, systems and methods that overcome challenges in the present art.